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copied!<p><code>==</code> compares the references. The intern method makes sure strings with the same value have the same reference.</p> <p>The javadoc for the <a href="http://download.oracle.com/javase/6/docs/api/java/lang/String.html" rel="noreferrer">String.intern method</a> explains:</p> <blockquote> <p>public String intern()</p> <p>Returns a canonical representation for the string object.</p> <p>A pool of strings, initially empty, is maintained privately by the class String.</p> <p>When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.</p> <p>It follows that for any two strings s and t, s.intern() == t.intern() is true if and only if s.equals(t) is true.</p> <p>All literal strings and string-valued constant expressions are interned. String literals are defined in §3.10.5 of the Java Language Specification</p> <p>Returns: a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.</p> </blockquote> <p>So without interning the compiler looks at the constants in the java code and builds its constant pool from that. There is a different pool maintained by the String class, and interning checks the string passed in against the pool and makes sure the reference is unique (so that == will work).</p>

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